1. Field of the Invention
The present invention relates to partially or fully neutralized mixtures of carboxylate functionalized ethylene copolymers or terpolymers (Mw between 80,000 and 500,000) with carboxylate functionalized ethylene low copolymers (Mw between 2,000 and 30,000). It also relates to the use of such ionomeric compositions in injection or compression molded applications such as golf ball components.
2. Description of Related Art
There is a need for highly resilient thermoplastic compositions that have good processibility without loss of properties or improved properties (improved resilience and lower stiffness) without loss of processibility.
There is a need in the golf ball art for balls that have a high resilience at high speed impact such as when struck by a driver and lower resilience at low speed impact such as when struck with a putter. High resilience at high speed impact would allow longer driving distance while lower resilience at low speed would provide better putting control.
The highly resilient thermoplastic compositions of this invention provide improved balance of properties and processibility. Also, based on testing of spheres, they appear to be useful as compositions in golf ball applications, particularly as cover and/or intermediate layer material or as core and/or center material or as a one-piece ball, to achieve high resilience at high impact speed and relatively lower resilience at lower impact speed.
The thermoplastic compositions are partially or fully neutralized xe2x80x9cbi-modal blendsxe2x80x9d of high copolymers/low copolymers. That is to say, they are melt-blends of ethylene xcex1,xcex2 ethylenically unsaturated C3-8 carboxylic acid copolymers having weight average molecular weights (Mw) of about 80,000 to about 500,000 (high copolymers) with ethylene xcex1,xcex2 ethylenically unsaturated C3-8 carboxylic acid low copolymers having Mw of about 2,000 to about 30,000 (low copolymers). The high copolymers may be blends of high copolymers and the low copolymers may be blends of low copolymers.
It has been found that, by proper selection of the low copolymer (AC540 has been found to be particularly useful), the thermoplastic compositions of this invention have demonstrated both enhanced melt processibility and enhanced heat stability. This combination of the property enhancements is contrasted to the reduction in heat stability that would be expected with higher melt flows. These unique bi-modal ionomer compositions are highly useful to the injection molding applications, including golf ball, foot wear, etc.
Further, with this proper selection of the low copolymer, the thermoplastic compositions of this invention are expected to have enhanced abrasion and scuff resistance. This property enhancement, together with the other property improvements described above, would be highly useful to injection molding, films applications, including golf ball, packaging films, flooring, protective coating, etc.
Preferably the weight percent high copolymer is about 50 to about 95 wt. % and the weight percent low copolymer is about 5 to about 50% based on the total weight of the high copolymer and the low copolymer. Preferably about 40 to 100%, alternatively about 50 to about 85%, of the acid moieties are neutralized by alkali metal or alkyline earth metal cations.
Optionally, the composition may contain up to 100 parts by weight of organic acid salts, up to 200 parts by weight thermoplastic elastomers, up to 170 parts by weight fillers based on 100 parts by weight of the xe2x80x9cbi-modalxe2x80x9d ionomer of high copolymer/low copolymer blend.
The compositions described above or their blends could be applied in broad end-uses applications, including injection molding applications, golf ball applications, etc. More specifically the compositions described above are most suited for golf ball applications such as the cover, intermediate layers, core, and center of 2- or multiple-piece balls, and as thermoplastic 1-piece balls.